1. Field
The embodiments described in the present specification relate to a semiconductor memory device and a method of controlling the same.
2. Description of the Related Art
A non-volatile semiconductor memory device such as a NAND flash memory comprises a memory cell. The memory cell comprises a control gate and a charge accumulation layer. The charge accumulated in the charge accumulation layer changes the threshold voltage of the memory cell. The amount of the threshold voltage is stored as data by the non-volatile semiconductor memory device. In such a semiconductor memory device, the threshold voltage may be dropped over time.